Fixed crash in xls export caused by off-by-one iterator
Fixed crash in xls export caused by off-by-one iterator

(this is for bnc#653533 and fdo#31141)

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core